This invention relates to a monitor for the level of salt in a water softener. More specifically, it relates to an automatic monitor that detects and indicates when the salt level in the brine tank is insufficient to completely regenerate the resin during subsequent regenerations.
While treating hard water, the ion exchange resin in a water softener absorbs calcium and magnesium ions from the water and replaces them with sodium ions. The resin becomes ineffective when the amount of available sodium is depleted and the resin is saturated with calcium and magnesium, and must be periodically regenerated. Water treatment is then suspended while the resin is regenerated in a multi-step process to flush the calcium and magnesium ions from the resin and restore the sodium level. The resin is first backwashed, by reversing the flow of the incoming water, to remove sediment. Next, the resin bed is contacted with a brine solution, whereby the resin takes sodium ions from the high concentration solution and displaces the calcium and magnesium ions into the brine. When an optimum amount of ion exchange has taken place, the brine solution and the unwanted hard water ions in it are discharged from the resin bed. After being rinsed to remove residual brine, the restored resin bed is then returned to service treating hard water.
Preparation of the brine solution takes place in a brine tank that is kept separate from the resin tank. The brine tank, which contains a supply of salt, is filled with water to form a saturated salt solution. The salt supply must be replaced periodically due to depletion of repeated regenerations. If the salt level is too low to make a brine solution of a given strength, there will be an insufficient sodium level to drive the exchange of calcium and magnesium ions and the resin will not effectively treat the hard water when it is placed back in service.
Generally, there is no automatic warning when the amount of salt is insufficient to restore the resin bed to an optimum ion exchange capacity. It has been left to the user to manually determine the salt level, usually by visually inspecting and estimating the salt level in the tank. Any manual determination of salt level is inconvenient for the user, who must frequently look into the brine tank. An inexperienced user may not know how much salt is required per regeneration, and create more work by adding salt too frequently or having hard water when salt is not added frequently enough.
To avoid having to make frequent visual inspections, users often prefer a softener unit with large salt capacity. Large units are more convenient, but also take up large amounts of space that may be prohibitive in small living spaces such as townhomes or condominiums. For areas where the softener unit may be visible, the exterior of some models is styled with an attractive cabinet-like finish. However, since this type of exterior finish is more expensive and, because they are generally used where space is a premium, the size of such units is usually small, requiring the user to frequently check the salt level.
The prior art provides an indicator stick, similar to a ruler, with reference marks to aid in judging the depth of salt present. Visual inspection is inaccurate even with reference marks, particularly when salt bridges are formed. While the brine is being made, the salt continuously dissolves and redeposits due to chemical equilibrium reactions. Salt bridges form when pieces of salt xe2x80x9cgrowxe2x80x9d together from salt deposition, and can make the volume of salt appear to be greater than is actually present. The salt under the bridge may be substantially dissolved, leaving only a small amount of salt in the tank even when a visual inspection from the top of the tank looks as if the salt bed has ample depth to complete additional regenerations.
Previous attempts to incorporate electronic monitors into water softeners have not proven satisfactory. Monitors were designed that utilized a weighted sensor on top of the salt to determine the salt level. However, if the operator forgot to remove the sensor when salt was added, the sensor would become buried, and falsely signal that the salt level was low.
A low salt level sensor utilizing a float is taught in U.S. Pat. No. 5,239,285, which is herein incorporated by reference. The salt level in this invention was determined by displacement of water. A predetermined amount of water was added to the brine tank, and if there was insufficient displacement of the water to push a float to a given level, the low-salt alarm was activated. However, this method requires that a portion of the apparatus be submerged in the brine, an environment that is corrosive and deposits salt on the equipment.
It is therefore an object of this invention to provide an improved monitor for the salt level in a water treatment device.
It is another object of this invention to provide an improved monitor for salt level that automatically checks the salt level without intervention from the user.
It is still another object of this invention to provide an improved salt monitor that provides an indication to the user when the amount of salt is too low to provide effective regeneration.
It is yet another object of this invention to provide an improved salt monitor that accurately indicates when salt should be added, even when salt bridges are formed.
The present invention provides an automatic monitor for use with a water conditioning apparatus. The improved monitor periodically checks the level of salt in the brine tank without intervention by an operator and provides a warning if the salt level is too low to effectively regenerate the ion exchange resin during the next regeneration cycle.
More specifically, the present invention provides an automatic monitor for use in a tank with a water soluble softening agent. The monitor includes a signal emitter that produces a signal capable of being detected by an array of signal-detecting sensors. The sensors are displaced generally vertically in the brine tank from the minimum depth of the softening agent to the maximum depth of the softening agent. The sensor produces an output in response to the signal.
The monitor also includes an electronic device for receiving and interpreting the output and determining if a low softening agent condition is present as the supply of the softening agent is depleted. An indicator warns when a low softening agent condition is present. Preferably, the sensors are linearly spaced within the tank.
The monitor of the present invention is advantageous to the user because it continuously monitors the salt level in the brine tank and provides a warning indicator when the salt level has dropped too low to successfully complete another regeneration. Continuous real-time monitoring of the salt level can also be achieved with the present monitor, if the electronics device that interprets the sensor output is programmed to do so. There is no need for the user to open up the softener cover on the brine tank to inspect the salt level. Even inexperienced users know from the indicator exactly when to add salt without having to guess if the amount of salt left is sufficient for the next regeneration.
The electronics of the present monitor are also optionally programmable to anticipate the calculated salt level, so that problems can be detected if the measured level differs significantly from the calculated level. Such differences can be indicators of salt bridges, faulty sensors or emitters, loss of eduction or overfilling of the brine tank. These features significantly improve both the convenience to the user as well as the accuracy of the reported salt level. Using a visual inspection of the brine tank, the user often has no way to tell that problems, such as salt bridges, exist below the surface of the salt bed. The present electronic monitoring system removes the inconvenience of repeated checking and the guesswork from maintaining an appropriate salt level in the water softener.